Scandium Phosphate Doped with Mn⁴⁺

The interaction between manganese dioxide and xenotime-structure ScPO₄ was studied by x-ray diffraction, IR spectroscopy, electron paramagnetic resonance, and luminescence spectroscopy. The results demonstrate that up to 1.5 wt % MnO₂ can be accommodated by ScPO₄ without structural changes. Mn⁴⁺ disproportionates by the reaction Mn⁴⁺ → Mn²⁺ + Mn⁵⁺ and is present in the structure of ScPO₄ in the form of the Mn²⁺ ion, substituting for Sc³⁺, and the MnO₄^3- ion, an analog of PO₄^3-. The presence of Mn³⁺, substituting isovalently for Sc³⁺, also cannot be ruled out. The manganese ions are shown to be rigidly fixed in the structure of ScPO₄.